1. Field of the Invention
The present invention relates to a high-frequency oscillator for use in, e.g., a receiving circuit of a satellite communication system.
2. Related Background Art
As a conventional example of a high-frequency oscillator of this type, there is the one described in a paper titled "AN EASY-TO-USE FET DRO DESIGN PROCEDURE SUITED TO MOST CAD PROGRAMS", 1989 IEEE MTT-S Digest, PP. 1,033-1,036. The arrangement of this high-frequency oscillator is diagrammed in FIG. 1.
A DRO (an oscillator using a dielectric resonator; Dielectric Resonator Oscillator) shown in FIG. 1 employs a MESFET (Schottky barrier field-effect transistor) Q1 as an amplifying element. A voltage Vd is applied to the drain of the FET Q1 through microstrip lines 1 to 4, and a voltage Vs is applied to its source through microstrip lines 5 to 8. A dielectric resonator is electromagnetically coupled to microstrip lines 9 and 10 on the gate, and this coupling circuit is expressed as a parallel circuit of L, C, and R. A high-frequency signal which appears at the drain of the MESFET Q1 is output through microstrip lines 11 to 14. The lines 13 and 14 constitute a capacitor, and a load resistor R.sub.L is connected to the line 14.
As described above, the signal output circuit in this conventional high-frequency oscillator has the microstrip lines 11 to 14 as its constituting elements. Accordingly, an area on a semiconductor substrate physically occupied by these lines 11 to 14 is increased to result in a large size of the oscillator as a whole. In addition, the signal output circuit having the above conventional arrangement has only a function of obtaining impedance matching. Therefore, it is impossible to allow the circuit to have, for example, a filter function of inhibiting transmission of signals having specific signal frequency components.